This lldb script lets you selectively ignore Obj-C exceptions. See http://chen.do/blog/2013/09/30/selectively-ignoring-objective-c-exceptions-in-xcode/

ignore_specified_objc_exceptions.py

import lldb
import re
import shlex

# This script allows Xcode to selectively ignore Obj-C exceptions
# based on any selector on the NSException instance
 

def command(debugger, user_input, result, unused):
    target = debugger.GetSelectedTarget()
    frame = target.GetProcess().GetSelectedThread().GetFrameAtIndex(0)
    filters = shlex.split(user_input)

    for filter in filters:
        method, regexp_str = filter.split(":", 1)
        value = frame.EvaluateExpression("(NSString *)[(NSException *)$rdi " + method + "]").GetObjectDescription()
        regexp = re.compile(regexp_str)

        if regexp.match(value):
            output = "Skipping exception because exception's {0} ({1}) matches {2}".format(method, value, regexp_str)
            result.PutCString(output)
            result.flush()

            # If we tell the debugger to continue before this script finishes,
            # Xcode gets into a weird state where it won't refuse to quit LLDB,
            # so we set async so the script terminates and hands control back to Xcode
            debugger.SetAsync(True)
            debugger.HandleCommand("continue")
            return None

    return None

def __lldb_init_module(debugger, unused):
    debugger.HandleCommand('command script add --function ignore_specified_objc_exceptions.command ignore_specified_objc_exceptions')